Automated electronics assembly machines are often used in the manufacture of printed circuit boards, which are used in various electronic devices. The manufacturing process is generally required to operate quite swiftly. Rapid or high speed manufacturing ensures that costs of the completed printed circuit board are minimized. However, the speed with which printed circuit boards are manufactured must be balanced by the acceptable level of scrap or defects caused by the process. Printed circuit boards can be extremely complicated and small and any one board may have a vast number of components and consequently a vast number of electrical connections. Printed circuit boards are now produced in large quantities. Since such printed circuit boards can be quite expensive and/or be used in expensive equipment, it is important that they be produced accurately and with high quality, high reliability, and minimum scrap. Unfortunately, because of the manufacturing methods available, some level of scrap and rejects still occurs. Typical faults on printed circuit boards include inaccuracy of placement of components on the board, which might mean that the components are not correctly electrically connected in the board. Another typical fault occurs when an incorrect component is placed at a given location on a circuit board. Additionally, the component might simply be absent, or it may be placed with incorrect electrical polarity. Further still, if there are insufficient solder paste deposits, this can lead to poor connections. Additionally, if there is too much solder paste, such a condition can lead to short circuits, and so on. Further still, other errors may prohibit, or otherwise inhibit, electrical connections between one or more components, and the board. An example of this condition is when a small, “stray” electrical component is accidentally released onto a section of the circuit board where another component is to be subsequently placed by another placement operation. This stray component may prevent electrical connectivity of the “correct” component that is placed onto the printed circuit board after the stray component. The condition if further exacerbated when the correct component has a package style, such as a ball grid array (BGA) or flip chip, where the electrical connections are visibly hidden after placement. In this condition, the stray component and the integrity of the solder joints cannot be visibly inspected either manually or by automated optical inspection (AOI) systems for errors or defects since the defects are hidden by the component package. X-ray systems may detect these errors, but these systems remain too slow and expensive for wide spread adoption in most printed circuit board assembly lines.
Conventional automated optical inspection systems receive a substrate, such as a printed circuit board, either immediately after placement of the components upon the printed circuit board and before wave soldering, or post reflow. Typically, the systems include a conveyor that is adapted to move the substrate under test through an optical field of view that acquires one or more images and analyzes those images to automatically derive conclusions about components on the substrate and/or the substrate itself. The amount of time to initially program the inspection inputs is often high for these systems and also to fine tune the inspection parameters or models. Another drawback to these automated optical inspection systems is that, although they can identify manufacturing errors, they often provide little help to identify the particular processes that caused the manufacturing error. As such, a need has arisen to provide an improved inspection system that simplifies the initial inspection programming as well as providing additional insight into the root cause of manufacturing errors.